The near extinction of one or both warring families. Feuding clans usually start with picking out the men of their opponents. When they begin to kill the women and children too, that's the sign that things are headed straight to hell and there will be no conciliating. Revenge by Proxy or Sins of Our Fathers are also bad signs.
They make peace. Sometimes they even intermarry to strengthen their arrangement. This has been known to happen in real life, surprisingly enough. In real life, there was also a practice to pay blood money to appease the family of the dead and end this vicious cycle. This rarely happens in fiction, though.
In Ghost Hound, the main and branch family, Komori and Ogami respectively, are at odds with one another, silently feuding despite two different generations trying to bring them together. Makoto and Tarou eventually overcome this.
In Naruto: The Senju and Uchiha clans were constant rivals during the Warring Clans Era, often seeking employment in conflicts simply to oppose one another. Eventually both clans grew tired of the bloodshed and formed an alliance, which led to the founding of Konoha and the end of open conflict between the two. Due to Madara's actions and the inherited distrust of the Uchiha, the Senju used their dominance in Konoha to effectively muzzle their rivals. The resulting discontent led to them planning a coup.
The origin of their feud is interesting in that it began when the two sons of the Sage of Six Paths fought over who was their father's rightful successor. The eldest and disinherited son was forefather to the Uchiha, and the favored younger son was forefather to the Senju.
Tobi has stated that Naruto, being a relative of the Senju, is destined to battle with Sasuke.
Basilisk, another Romeo and Juliet between feuding ninja clans who had been in a tense peace until given a reason. And anyone who didn't have a personal reason before, gets one.
The Tennos and Sanzenin families of Hayate the Combat Butler are said to have this kind of a relationship, hinted at being a rivalry of fortunes. What with only one person of child-bearing age each and both of them after the same guy, it's likely one of the families will die out, if not both.
The title characters of Noir end up taking a contract on an ex-KGB officer who had ordered genocidal purges on a specific ethnic group some decades before. It turned out that this particular incident was just the last atrocity committed between that ethnic group and the officer's ethnic group in a feud that had been going on for centuries. The ultimate cause of this feud was never mentioned.
In Wild Rock, although they avoid bloodshed, the lake clan and the forest clan have tense relations because their natural hunting grounds overlap. Thanks to Emba's prowess the forest clan is not getting much meat at all, hence Yuuen gets sent on a Honey Trap mission to convince Emba to give him some of his catch. In the end Yuuen's and Emba's genuine feelings for each other lead to the clans setting aside their rivalry and uniting, and Yuuen's and Emba's siblings get married.
Scare Tactics included a generations old feud between the Ketchums (a clan of werewolves) and the Knightsbridges (a family of ghouls).
Lucky Luke's episode "The Rivals of Painful Gulch."
A major plot point in Nikolai Dante is the feud between the Romanovs and ruling Marakovs. When this erupts into all-out war, Nikolai is forced to fight against his lover, Jena Marakov, due o conflicting loyalties.
The two big speedster families of The DCU, the West/Allen line and Thawne line. Bart Allen - Impulse/Kid Flash II - is an heir to both, and aware of it, but totally neat in he doesn't angst over his lineage like most other people (he doesn't really think or talk about it unless you insist on pressing the issue) and practically laughs at Zoom's "corrupted bloodline" rant.
Played for Laughs in the BritishAnthology ComicThe Beezer with the strip the Hillys and the Billies about two feuding families of Hillbillies. The Beano also featured feuding families in a strip called The Three Bears which would occassionally feature a feud between Ma, Pa and Ted bear (the eponymous three bears) and Grizzly Gus and his family.
Sean Russell's Swan's War books: The eponymous swan is the heraldic animal of both the feuding families, the Rennes and the Wills. Their feud lasts centuries and is partially fueled by an ancient curse, partially by the fear that if one of them stops fighting, the other will destroy them. Unusually, there seems to be no real hatred between them anymore and it's repeatedly stressed how profoundly battle-weary they are. In the end they make peace through marriage of their family heads and it seems the next heir to those posts will be a Renne-Wills.
Venezuelan novel Doña Bárbara averts this. While in the backstory is mentioned the long rivalry of the Luzardo with the Barquero. the protagonist, Santos Luzardo (a character so perfect he almost is a Mary Sue) ends the feud with Lorenzo Barquero, both of them the last of their family.
Dune. In fact, feuding families are so prevalent in the Dune universe that it has evolved into an art form. There's "Kanly," which is one-on-one combat, and the all-out War of Assassins, which is just what it sounds like. The rules are codified in the Great Convention, which sets out exactly who are the acceptable targets and what weapons or poisons are permitted. Noble families in the Dune universe accept the fact that you can be knifed in the back at any time as just another hazard of the job.
The feud between the Venturi and Selachii families has escalated to ridiculous levels; in social situations, should members of both families meet, their attempts at acting courteous involves conversations on which there can be no disagreement. Given their history, this has become "a very small number of things." Whatever started the feud is long forgotten, but is naturally assumed to be something tremendously huge, or else it would be silly to keep it up like that. To illustrate further just how far it has gone the aforementioned small number of things acceptable to talk about boils down to mentioning people are standing upright at a party and that the horizontal position, while not done for the social occasional, has its uses. (Genius Bonus: a Venturi pipe is a kind of pressurised outflow pipe, and selachii is the scientific name for the shark and dogfish family. They're the Sharks and the Jets.)
The various branches of the Ogg family:
They are also constantly mid-feud, a fact that has caused some people to try and feud with an Ogg, which results in the ENTIRE Ogg family turning on them.
It's noted that the main reason for Ogg family infighting is because Nanny Ogg deliberately provokes them into feuding with one another, mostly to relieve her boredom between supernatural crises.
The Starks and Lannisters. The only reason they are civil to each other is because Ned Stark's best friend Robert Baratheon married into the Lannister family. But once Robert dies (and it's strongly hinted at the his wife Cersei killed him), all bets are off and the Lannisters utterly devastate the Starks, though not without suffering some losses themselves. It's worth noting that Martin based this feud lightly on the Wars of the Roses.
A more civil example exists between Houses Tyrell and Martell - while not openly hostile towards each other like the Starks and Lannisters, they have a long enmity dating back centuries that they're still not entirely over today. They mostly get by using passive-aggressive digs at each other and giving whoever's in charge of dealing with them when they're in the same place a headache. A notable exception is Willas Tyrell and Oberyn Martell, who are pen pals who get along nicely, despite being the pretext for the current generation's mutual hatred; Oberyn crippled Willas in a tournament, and even though it was a fair match and a complete accident caused largely by Non-Action Guy Willas being in a fight he had no business being in, the only Tyrell not to blame Oberyn (and thus the entire Martell family,) is Willas himself.
Riverlands families Bracken and Blackwood loathe each other, to the point that Lord Tytos Blackwood refuses to surrender despite his castle being his side's last remaining stronghold in a war, because it means he'll be surrendering to the Brackens. When Jaime Lannister comes along and offers more amicable terms, he's quick to surrender. While there Jaime inquires why the two families have never tried to make peace, and it turns out they have made peace dozens of times and are so intermarried every Blackwood has a Bracken ancestor, and visa versa. Eventually the people who made the peace die, and something reinvigorates the feud.
Although initially rather one-sided, the Freys have loathed their titular overlords the Tullys for quite a while and stalled them wherever feasible using mainly Passive-Aggressive Kombat of various kinds and ducking behind Plausible Deniability whenever possible without actively breaking their connections. They ramp their end of the feud up by several orders of magnitude thanks to the Red Wedding, so it actually becomes this trope good and hard with any surviving (or undead) Tully and their allies quite motivated to join in.
In the novel Imzadi, two planets have been hostile—not open warfare, but anger and resentment—for generations, until a window into the past reveals the extremely trivial origins of the hostility (A dog analogue owned by an official from one planet killed a cat analogue owned by an official of the other, which resulted in the first ever peace treaty to include a section about leash laws). It's played exactly like Feuding Families.
In the Star Trek: New Frontier novel "Martyr," the Unglza and Eenza tribes of the planet Zondar had been at war for over 500 years, and Calhoun's arrival was predicted to usher in peace. Then in "Cold Wars" in the Gateways series, the Aerons and Markanians had been separated warring for the "sacred world" of Sinqay, with the Gateways recently renewing their hostilities, until the Excalibur and Trident actually return them to their "sacred world," now an uninhabitable black rock. Does This Remind You of Anything?, Israel and Palestine?
Q-in-Law featured a pair on massive space ships, literally making Enterprise the man in the middle, trying to provide neutral ground for the intermarriage. Since Q is around, it definitely does not go as planned. A case of Hilarity Ensues done well.
One of the Nightside books involves a Romeo and Juliet type situation where the couple persuade their families to call a truce and get married, only to both be murdered at the wedding dinner.
Kushiel's Legacy has a gradually building example of this. In Kushiel's Scionone of Imriel's reasons for sitting on the information that cousin Bernadette de Trevalion tried to have him killed is to try to end the Cycle of Revenge; his mother was responsible for the disgrace of her and her husband's families.
In The Godfather, Vito Corleone promises not to take revenge after the death of Sonny, as he is tired of the continuous cycle of murders. When Vito dies, Michael is free to eliminate pretty much every other Don who ever posed as rivals, plus a few traitors in his own family, leaving the Corleone's in sole control of the city.
Likewise, Mario Puzo's The Last Don begins with Don Clericuzio agreeing for his daughter to marry Jimmy Santadio, the son of his rival. Don Clericuzio then has Jimmy and Jimmy's family murdered on the wedding night.
The short story The Interlopers is about the end of such a feud.
Saki's "The Blood-Feud of Toad-Water, a West-Country Epic" satirizes such feuds.
In The 39 Clues, the fued is going on between different branches of the same family, but characters from different branches are only very distantly related. In the tenth book, there is also mention of another family who wants to gain Cahill secrets, hinting that if a second series is made, there will be a fight between the Cahills and Vespers.
In one of the books, two feuding families have been going at it for generations. One side even cursed the other so that female children are sometimes born as mermaids who cannot conceive. This all comes to a crashing halt when one side gets a hold of Farslayer, a sword which does exactly what it sounds like it should do. Most of the two sides are wiped out in one night.
To clarify: Farslayer is a magical sword, which can fly towards any target the wielder uses and slay it, no matter how far away. The catch is, once Farslayer hits the target, it stays there. Where it is free for the target's kinsmen to pick it up and retaliate. Rinse and repeat until there's no one left to aim at.
L.A. Banks's short story "Spellbound" has the two families practicing voodoo, making things complicated when the newest generations meet at college and fall in love.
Raymond E. Feist and Janny Wurts' Empire Trilogy. In the first two novels, Daughter of the Empire and Servant of the Empire, the Acoma and Minwanabi families are long-term enemies who seek to destroy each other while remaining within the laws and customs of the Empire. In the third, the Acoma are triumphant, but they have to deal with two new feuds that started due to their war with the Minwanabi.
Perhaps inevitably, The Beverly Hillbillies had one of these, after Sonny Drysdale refuses to marry Elly May in a first-season episode.
The Ewings vs. Barnes intergenerational feud in Dallas. As of the latest revival of the show, the feud has been going on for approximately 80 years and its still going strong into the third generation.
In the Charmed episode "Love's a Witch," Paige has to play mediator in a feud between two magical families.
There's an entire Super Sentai based around the concept, namely Rescue Sentai GoGoFive, wherein the Tatsumis, a family of rescue workers, battle the Saimas, a family of demons who cause natural disasters.
Coronation Street has this as a stock plot, and for some reason it seems to keep happening to the Platts. First there was feud with the Windasses which ended when David got Gary sent to prison. Currently there seems to be a feud between the Barlow's and the Platt's which started when Tracy Barlow lied to incriminate Gail for murder, while she was serving time herself and trying to cut a deal. It continued when Deirdre tried to steal Audrey's(Gail mum) boyfriend, only to have him turn around and steal four grand from her stepson Peter's business. With it recently being revealed that Gail's son Nick was having an affair with Peter's wife this feud looks to be continuing for quite a while yet.
The Starks and Lannisters in Game of Thrones. As of the end of season one, they are at war.
CSI NY had a first season episode with feuding circus families that led to a suicide pact.
The blood feud of American history - Hatfields And Mc Coys - just got its own miniseries on the History Channel.
Occurs in Grimm. Grimms have been killing wesen for centuries and those families can hold grudges. Monroe's grandfather was killed by a Grimm and he is afraid he would be disown if his family finds out that he is friends with Nick, a Grimm.
Some supernatural species don't get along, such as the Blutbad and Bauerschwein, wolves and pigs respectively. Bauerschwein has been victim to Blutbad violence and in "Three Bad Wolves", one has had enough and killed the brothers of the Blutbad who had killed the Bauerschwein's brothers.
Dungeons & Dragons 1st Edition supplement Oriental Adventures. If a character was created under the OA rules, their family could have an Ancestral Feud with another family. When any member of the character's family meets a member of the other family they have a significant reaction penalty to each other and the two are much more likely to be hostile to each other. This can result in insults, a duel or even an outright attack.
The Kusanagi vs. Yagami feud in The King of Fighters. Although they both sealed Orochi, the Kusanagi got more recognition and fame, which provoked the Yagami to cut a deal with Orochi for the ability to wield flames like the Kusanagi.
As a game revolving around playing feudal housesin space, Imperium Nova features a mechanic called feud score that regulates family feuds. Feud score is created through spying, attempted assassinations, military attacks, insults, and other hostile actions. Attacking another house without the proper feud causes you to become a renegade and, theoretically, an instant pariah.
The Goodsoups and the VanSalads in The Curse of Monkey Island were feuding families both in the hotel business, but the Vansalads were eventually driven out of the Carribean.
The Montys and the Capps in The Sims is based off the Montagues and the Capulets; the reason why they started the feud was due to the Monty Patriarch losing a promising job as an associate with the Capps.
The Battle-Borns and the Greymanes in The Elder Scrolls V: Skyrim were once close, but after the Civil War they became bitter enemies, with the Battle-Borns supporting the Empire while the Greymanes support the Stormcloaks.
The Zafords and Hodunks are in a truce over their feud at first in Borderlands 2, but ex-Hodunk Ellie decides the world would be better off without them and has you set off the feud and let you decide which family survives.
In Dragon Age, the Couslands and the Howes have a complicated history, fighting on opposite sides during the Orlesian occupation of Ferelden. While close allies in the present, Arl Howe later betrays Teyrn Cousland out of jealousy and orchestrates the murder of the entire family save for (potentially) the Human Noble and Fergus Cousland.
In Awakening, if importing a save with the Human Noble Warden, this adds additional subtext when Nathaniel Howe attempts to murder the Warden to avenge the death of his father and the loss of his family lands to the Grey Wardens. Nicely subverted however, as the Warden can decide to end the blood-feud by recruiting Nathaniel into the Wardens and befriending him.
This was added to Crusader Kings 2 in The Republic DLC. Appropriate given how the game is all about dynasties instead of nations.
There's one in The King Of Dragon Pass: Rangarda Dark-Eyes, who is from another clan, has her sons steal the Cool Horse Tempest from Glendara, a woman in your clan. Glendara has her kids reclaim the horse, but they'll kill one of Rangarda's sons during the rescue. And from there on it erupts into a full-on Cycle of Revenge: the two families will try to kill each other, burn down their houses, destroy their property, and so on. And nothing you do can ever stop the feud, short of killing note This includes killing Rangarda's grandsons while they are still children, which will provoke the other clan into a feud and destroy your own clan's morale or outlawing everyone involved. The most you can do is try to maintain a good relationship with the other clan. Fortunately, the whole mess is started by a Random Event, so if you're lucky it may never happen at all.
In The Gamer's Alliance, the Jardines and Mathesons are two powerful noble families, each of which controls one big city. They hate each other's guts and are often literally at each other's throats if given time. This animosity goes so far that if one of them joins a large faction like the Grand Alliance, the other will automatically oppose the alliance even if it means siding with a faction they would normally consider their enemy.
A mechanic of Imperium Nova, houses gain feud points against other houses who offend them via insults, ignoring monopolies or trade restrictions, destroying facilities, or assassinations. Feud is required for houses to attack one another on planets under imperial jurisdiction and is expended with every successful assault. It's not unknown for players to intentionally insult one another so the mechanical feud can persist as long as the RP one.
The Zhang vs the Gan Jin from Avatar: The Last Airbender. Their animosity is played for laughs, and in the end they're tricked into making peace by Aang.
Make Mine Music, from the Disney Animated Canon, had a segment titled "The Martins and the Coys" which featured the popular radio vocal group, King's Men singing the story of a Hatfields and McCoys-style feud in the mountains broken up when two young people from each side fall in love. This segment was later cut from the film's video release due to comic gunplay.
The Flintstones episode "Bedrock Hillbillies" has Fred inheriting a shack in the mountains and getting caught up in a longstanding feud between his ancestors and the Hatrock clan. It turns out it all started when Fred's ancestor made fun of a painting of a Hatrock matriarch and the family was murderously insulted. Eventually, the families managed to make peace, at least until Fred saw the painting himself and unknowingly made the exact same wisecrack and restarted the feud, forcing the Flintstones and Rubble to flee back to Bedrock.
The McCoys and Weavers, in the 1938 short A Feud There Was.
The McCoys and Martins, in the 1939 short Naughty Neighbors. The feud is broken up by a "non-aggression pact" (an allusion to then-looming World War II) signed by the respective heads of the families (Porky and Petunia Pig).
Woody Woodpecker: By the time Woody got involved, the Coys were already extinct and the last one's house became a museum of family memorabilia. Woody put on a Coy's hat and the last Martin assumed Woody was a Coy.
According to Word of God the Canmore and Monmouth families in Gargoyles would have become this, stemming from each one's attitude toward gargoyles. Jon Canmore's side of the family would have been strongly opposed to gargoyle integration in society whilst his sister Robyn (having married Harry Monmouth (a.k.a. Dingo) would have supported it.
More Real Life: The Pazzi family and the Medici family of Renaissance Florence, Italy. The former is famous for their botched assassination attempt on Lorenzo and Guiliano de' Medici on April 26, 1478 after High Mass on the steps of the Duomo. To be fair to the Pazzi family, The Pope didn't like the Medicis either. Not many people did, except the people of Florence.
And thus, the inspiration for the first arc of Assassin's Creed II. Only the main character is on the Medicis' side.
The real war was not as bad: any class below the nobles and royals was relatively unscathed, the Yorkists destroyed the Lancastrians without much of a struggle (mostly because their leader was insane and Ambiguous Disorder), and Henry VII eventually ended the war with one battle and stopped any more conflicts from starting.
The German branches of the House of Welfs and the House of Hohenstaufen in the 12th century. Not even marriage between them could end it, though both families were much too large and powerful to actually die out from a mere feud.
In the second half of the 19th century the House of Welf got into a feud with the House of Hohenzollern after The Kingdom of Prussia (under the Hohenzollerns) annexed the Kingdom of Hannover and drove the Welfs in exile in Austria. This feud was resolved in the classical way in 1912, when the last surviving son of the head of the Welfs met and fell in love with the only daughter of the head of the Hohenzollern family.
The Japanese have had a bunch of these. Several of which led to country wide civil wars. Most famously the Gempei war between the Taira (Heike) and the Minamoto (Genji) clans.
The Vikings of the Scandinavian lands were infamous for this. They would always fight each other for even the smallest things. The only thing that would make temporary truces was to invade England or France. It was only when Christianity came to the northern lands, and then the Viking chieftains took inspiration from the feudal systems in the mainland and reformed their turfs into united kingdoms, that the feudings ended.
In several Italian city-states one of the requirements of citizenship was to forswear vengeance as that supposedly now belonged to The Government which was supposed to dispense it impartially. The fact that that had to be made explicit reveals a number of things about Medieval Italian culture.
In Korea, the Shims and the Yooms. The feud started in the mid 1700's and went on for about 250 years.
A more lighthearted version of this is from many British regiments. The British military system still maintains traces of the eighteenth century warrior fraternity air in an age of heavily bureaucratized warfare. Several regiments are traditional "enemies" and will continue their feuds with practical jokes and bar brawls.
Similar ritual feuds have been noted by anthropologists among low-tech cultures. As lethal weapons are sometimes used the proportion of ritual and the proportion of feud is debatable and in any case probably depends on the nature of the dispute.
Oddly enough potential feuding does have a positive (or at least less negative) side effect in serving as a substitute for military and constabulary deterrence in places where The Government is weak. In such places a common custom is to pay blood-money for cross-tribal offenses weighted at the economic or political value of the person injured. This provides a face-saver that allows The Patriarchs of a given clan to settle the dispute without a feud, but the threat of feud remains a feature of local politics.
The Bavarian town of Herzogenaurach, located about 15 miles northwest of Nuremberg, is today considered one of the greatest laboratories for sociologists thanks to a local family feud that has since expanded to ridiculous proportions. It all started in 1924 when hometown boys Adolf "Adi" Dassler and his brother Rudolf opened an athletic shoe company which is today known as Puma. The Dasslers achieved worldwide fame when Jesse Owens ran in their shoes when he won several gold medals at the 1936 Olympic Games. But the Dassler boys - the biggest employers in town - hated each others' guts, and their hatred for each other only grew worse during World War II. In 1948, the brothers announced to their workers that their hatred for each other had reached an irreconcilable point and that Adi was leaving to open a rival company – Adidas - on the other side of town, across the Aurach River. The employees then started choosing sides. After a quarter century, most of the people in town had relocated themselves to the side of the river that corresponded with whichever company they favored. Now the town - which had been united for over 900 years – is like a house shared by two pissed-off divorcees who refuse to move out after everything else has been settled. Except that instead of two people, there are about 24,000 people. Today, each side of the river has its own businesses, athletic teams, schools, etc. And if you wear Pumas on the Adidas side of the river, or vice versa, you probably won't get served at local businesses, you probably will be heckled, and you may be assaulted.
The clans of Scotland were known for this for a long time, though it died down after the country's acquisition by the United Kingdom, which served to unite many of them to rebel against a perceived common enemy.
Not, however, the Mac Donalds and Campbells, whose feud fed into the Jacobite wars, and was maintained into modern times by the Gordon and Argyll Highlander regiments of the British army.